The present invention generally relates to memory storage devices of the type that include one or more rotating discs. More particularly, the present invention concerns rotating disc memory storage devices that include a housing that provides a dust-free environment for the rotating disc or discs.
U.S. Pat. Nos. 4,280,155 and 4,282,554 are illustrative of that type of rotating disc memory storage apparatus known as fixed disc drives. As shown in the '554 patent, a fixed disc drive typically includes a housing made of two generally bowl-shaped casings that are fastened together to form an air-tight seal therebetween so that the discs are isolated from the ambient environment. Such air-tight seal is desirable because the presence of dust or other air-borne contaminants on the active portions of the discs will introduce noise into read-out therefrom and will also induce rapid wear of the transducers and disc surfaces. It is also noted that the motor of the disc drive devices include air-tight bearing seals to further reduce the possibility of dust contamination, and also a filter is incorporated in the internal ventilation or cooling system of the device (as illustrated in U.S. Pat. No. 4,282,554) to remove any contaminants from air recirculated within the housing.
The aforementioned U.S. Pat. No. 4,280,155 discloses a fixed disc drive that includes a flat rectangular base plate made of aluminum and a bowl-shaped cover made of plastic. A magnetic transducer head carriage and positioning assembly (referred to hereinafter as a transducer actuator assembly) is mounted to the base plate adjacent the periphery of the discs, with the transducers being mounted upon flexure arms that project outwardly form the actuator assembly. The motor for rotating the discs is mounted above the base plate within the housing.
Although prior known fixed disc drives have been generally satisfactory, some have been subject to resonant vibration problems. For example in some larger drives, the rapid reciprocation of the actuator assembly thereof induces vibrations that are large enough to cause visible movement in the housing. In many drives it is found that the resonant vibrations induced by normal reciprocation or stepping action of the actuator assembly, while not causing visible oscillations in the housing, nevertheless are great enough to cause the transducers to oscillate with a substantial amplitude to create an out of phase error signal. It will be understood by those of skill in the rotating disc memory storage art that this sort of oscillation must be minimized so that the stability of the closed loop servo can be maintained. Of course, if the width of the track locations on the disc storage memory device is relatively narrow, the number of tracks on the disc will be greater. Thus, the so-called track density of a disc drive can be increased by minimizing the track width. However, due to the resonance-induced oscillations of known prior art fixed disc drives, the prior art servo systems have sometimes been unable to hold a transducer on a desired track or to lock on to a desired track.
A major object of the present invention is to provide a rotating disc memory storage apparatus wherein the base plate resonant vibrations induced by reciprocation of the actuator assembly are substantially dampened so that there is no base plate motion for the closed loop servo system to respond to.